A standard for wireless local area network (WLAN) technology is being developed as an IEEE (Institute of Electrical and Electronics Engineers) 802.11 standard. IEEE 802.11a and b use an unlicensed band at 2.4. GHz or 5 GHz, and IEEE 802.11b provides a transmission rate (or transmission speed) of 11 Mbps, and IEEE 802.11a provides a transmission rate of 54 Mbps. IEEE 802.11g provides a transmission rate of 54 Mbps, by applying Orthogonal Frequency Division Multiplexing (OFDM) at 2.4 GHz. IEEE 802.11n provides a transmission rate of 300 Mbps with respect to 4 spatial streams, by applying Multiple Input Multiple Output-OFDM (MIMO-OFDM). And, IEEE 802.11n supports a channel bandwidth of up to 40 MHz, and, in this case, IEEE 802.11n provides a transmission rate of 600 Mbps.
A standard for regulating operations of an unlicensed device in a TV whitespace (TVWS) band corresponds to an IEEE 802.11af standard.
As a frequency being allocated to a broadcast TV, TVWS includes a UHF (Ultra High Frequency) band and a VHF (very high frequency) band, and the TVWS refers to a frequency band that is authorized to use unlicensed devices under the condition that the corresponding frequency band does not impede (or hinder) the communication of licensed devices operating in the corresponding frequency band. Licensed devices may include TVs, wireless microphones, and so on. A licensed device may also be referred to as an incumbent user or a primary user. Additionally, in order to resolve the problem of coexistence between unlicensed devices using the TVWS, a signaling protocol, such as a common beacon frame, a frequency sensing mechanism, and so on, may be required. Unlicensed devices operating in the TVWS may be classified as Fixed Devices, Personal/Portable Mode I devices, Personal/Portable Mode II devices, and so on. As a fixed-type user equipment, the Fixed Device is required to register its position in a geo-location database, and the Fixed Device may obtain an available channel list by accessing the geo-location database. The Fixed Device operates in the corresponding available channel list, and, if a channel that is being used by the corresponding Fixed Device is no longer available, the usage of the corresponding channel is suspended. As a personal portable user equipment, the Personal/Portable Mode II does not register its position in the geo-location database, however, the Personal/Portable Mode II may obtain an available channel list by accessing the geo-location database. The Personal/Portable Mode II device operates in the corresponding available channel list, and, if a channel that is being used by the corresponding Personal/Portable Mode II device is no longer available, the usage of the corresponding channel is suspended. As compared to the Fixed Device, a transmission output power is limited. The Personal/Portable Mode I device is controlled by the Fixed device and the Personal/Portable Mode II device. And, just as the Personal/Portable Mode II device, although the Personal/Portable Mode I device does not register its position in the geo-location database, the Personal/Portable Mode I device may carry out a validity verification process respective to its device ID through the geo-location database, so as to be authorized for usage. Additionally, the Personal/Portable Mode I device is required to obtain the available channel list from the Personal/Portable Mode II device, and the Personal/Portable Mode I device should periodically verify that the available channel list remains unchanged.
Although in 512˜608 MHz and 614˜698 MHz, the operation of all unlicensed devices is authorized with the exception for a few special cases, in bands of 54˜60 MHz, 76˜88 MHz, 174˜216 MHz, and 470˜512 MHz, only the communication between fixed devices performing signal transmission in pre-decided locations is authorized. An IEEE 802.11 TVWS user equipment (or terminal) refers to an unlicensed device that is operated by using media access control (MAC) and a physical layer (PHY).
Table 1 shown below shows a comparison between a performance of IEEE 802.11ac PHY and a performance of IEEE 802.11 of PHY. The IEEE 802.11 of PHY, which uses the IEEE 802.11ac PHY that is processed with 1/10 down-clocking, provides 2 MHz/4 MHz/8 MHz/16 MHz/8+8 MHz channel bandwidths. In case of performing 1/10 down-clocking, a Guard Interval (GI) increases from 0.8 us to 8 us.
TABLE 1IEEE 802.11ac PHYIEEE 802.11af PHYChannelChannel bandwidthThroughputbandwidthThroughput2086.728.674020042080433.3843.33160866.71686.6780 + 80866.68 + 886.66